DHCP Server priority choice

Unanswered Question
Jul 14th, 2010

Hi expert,

Refer to my attached diagram, Can I setup that when LAN user want to get IP address from DHCP server, first choice will query dhcp server. Once dhcp server is down, then will query dhcp server.

thank you

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Dipesh Patel Wed, 07/14/2010 - 06:27


Yes you can.

For this you need to add following cmd on LAN segment vlan int.

int vlan XX

ip address ...................

ip helper-address

ip helper-address

If you have any doubt, pls post config.

than I can tell you where exactly need to add these cmds.

Hope this will help you

Rate the post if it will help you.


acbennyma Wed, 07/14/2010 - 06:37

Dear sir,

You mean below configuration can make me to request dhcp request from first, once server is down, it will drop to the second one ?

My configuration is

int vlan 100

ip address

ip helper-address

ip helper-address

Then if I change to

int vlan100

ip address

ip helper-address

ip helper-address

that means first query dhcp server first, once is down, it will query to ?

Any document has publish  it ?


Richard Burts Wed, 07/14/2010 - 07:34

Unfortunately Dipesh is incorrect when he says that you can specify a DHCP server to querry first. If you configure 2 ip helper address commands then IOS will forward requests to both of them. It is likely that both will respond and in that case the client usually accepts the first one that responds. There is not a way in IOS to achieve what you want, that the request will go to a primary and only if that one is down will go to a secondary.



acbennyma Wed, 07/14/2010 - 07:43

Dear sir,

You mean there is no way to control what is first and what is second, Client receive IP address is base on which dhcp respond is faster. Am I right ?

Richard Burts Wed, 07/14/2010 - 09:20

Yes you are right. With ip helper-address there is not a way to establish priority.



Dipesh Patel Wed, 07/14/2010 - 21:36


I am not saying the priority of helper address.

But the reachability to DHCP server.

Suppose One DHCP server is in other segment and one DHCP server in the sane local segment than the dhcp server in the local segment will reponse first.

for 172.X.X.1 is other side of router so it will be reached second. 1st will use the dhcp server on local segment and if it will down than go for second one.



This Discussion